This invention relates to a valve assembly designed to be coupled to a trailer brake air line a trailer or the like to prevent a driver from deliberately or inadvertently moving the trailer from a parked position without an affirmative step being taken by a person in control of the trailer, such as a dockman in charge of loading or unloading the trailer.
Several devices are known in the art to provide protection for truck trailer brake assemblies. U.S. Pat. No. 4,621,874 relates to a vehicle theft preventing device acting on the brake system. The system includes a locking device comprising a three-way valve coupled an air line of the brake system. In an anti-theft arrangement, the valve directs air pressure supplied to the brake system from the tractor away from parking brakes and toward front brakes of the trailer so that no air is supplied to release the parking brakes.
U.S. Pat. No. 4,543,984 discloses a truck trailer brake airline lock. The lock is situated in a housing permanently attached to the front end of the trailer. The housing contains a valve which is actuated to maintain air pressure in the airlines of the brake system even after the truck is unhitched from the trailer and driven away. The trailer stays in place with air in its brake lines which maintains the brakes in an engaged position to inhibit theft of the trailer. This system is not used with spring biased brakes which require air pressure to release the brakes.
U.S. Pat. No. 4,593,954 discloses an air brake valve system which places all of the valves required at each axle within a single housing to produce a neater installation beneath the trailer chassis. This patent illustrates the 121 brake system which has been standard since 1975.
Parking or emergency air brakes on a trailer are typically biased to a normally engaged or locked position by a spring to lock the wheels on the trailer at times when air pressure is not supplied to an air line to release the brakes. The tractor or truck used to haul the trailer includes an air compressor which provides an air supply for releasing the brakes through a brake air line. This brake air line for controlling the parking and emergency brakes is typically referred to as the "red line". The "blue line" brake air line delivers air pressure to another portion of the trailer brakes to engage the brakes when a driver presses on the brake pedal in the truck.
When a trailer is parked at a loading dock or at another location, the truck is often removed from the trailer. Therefore, the air supply to the red line is removed. When the air supply is removed, the air brakes are biased to their normally engaged or locked position by the spring to lock the wheels to prevent movement of the trailer.
Numerous accidents occur each year when a trailer is left parked at a loading dock. Every so often, a driver will connect a truck to the parked trailer and hook up the air hoses to connect the air compressor to the brake lines of the trailer. Air pressure added to the red line releases the air brakes. The driver can then move the trailer from its parked position. Drivers are often responsible for hooking up their trucks to various trailers after the trailers have been loaded with cargo and moving the loaded trailers to another position on the lot. If the driver hooks up to the wrong trailer and moves the trailer before the dockman in charge of loading the trailer is ready, persons loading an interior portion of the trailer with cargo can be injured.
One object of the present invention is to provide a valve assembly coupled to the brake system of the trailer to prevent movement of the trailer without the cooperation from the dockman to adjust the valve assembly.
Another object of the present invention is to provide a warning system to alert workers in the trailer or a dock area that someone is attempting to move the trailer prematurely so that the workers can take precautionary measures.
According to the present invention, an assembly is provided for use with a trailer for holding cargo, a plurality of wheels, normally engaged air brakes coupled to the wheels, and an air supply line coupled to the air brakes for supplying air to release the air brakes. The assembly includes valve means for selectively venting the air supply line to the atmosphere to prevent the release of the air brakes from their normally engaged position. The valve means is coupled to the air supply line. The valve means is adjustable between a first position and a second position. In the first position, the valve means seals the air supply line to permit the air brakes to be released when air is supplied to the air supply line. In the second position, the valve means vents the air supply line to the atmosphere. When the valve means is in its second position and air is supplied to the air supply line, the air is vented to the atmosphere. Therefore, in the second position, the valve means prevents the air brakes from being released when air is being supplied to the air supply line.
In the illustrated embodiment of the present invention, the valve means is coupled to the trailer and configured so that the valve means is accessible and adjustable from within an interior region of the trailer. This permits the dockman to adjust the valve means between its first and second positions from the interior region of the trailer. Therefore, the dockman can have control over whether the brakes can be released. By giving the dockman control, the present invention advantageously reduces the likelihood that the trailer will be moved while workers are still loading the interior region with cargo. The valve means is preferably located near a rear door of the trailer so that the dockman can open the valve as soon as the rear doors are open, even with a full load on the trailer. The valve can remain open until cargo is unloaded from or loaded onto the trailer. By placing the valve means near the rear door, workers can load the trailer full of cargo while the valve is open. The dockman can then close the valve means just prior to closing the rear doors of the trailer.
Also in the illustrated embodiment, the assembly includes alarm means coupled to the valve means for providing an audible indication when air is being vented through the valve means to the atmosphere. When workers loading the interior region of the trailer hear the alarm sound, the workers can take precautionary measures, to reduce the risk of injury. The alarm means also alerts a driver that the valve is in its second position and that workers may be still loading the interior region of the trailer with cargo so that the driver will not attempt to move the trailer.
In this specification and in the claims, the word "trailer" is intended to refer to various types of trailers, flat beds, or trucks in which the driver is blind to cargo which use a 121 type air brake system or other brake system similar to the 121 system.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.